MESOSCALE PRECIPITATION DISCUSSION 0550
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
833 AM EDT MON JUL 24 2017

AREAS AFFECTED...NORTH CENTRAL NEW YORK

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 241232Z - 241732Z

SUMMARY...LOW INSTABILITY BUT VERY STRONG MOISTURE CONVERGENCE AND
SLOW CELL MOTIONS PRESENT FLOODING CONCERN THIS MORNING.

DISCUSSION...GOES-E WV LOOP DEPICTS A VERY STRONG VORT MAX ACROSS
SE ONTARIO THAT IS SWINGING A BIT NEGATIVE TILT SUPPORTING A
SECONDARY SHORTWAVE TO AMPLIFY ACROSS S CENTRAL NY.  THIS ALLOWS
FOR A STRONG STACKED SFC TO 7H LOW ACROSS E LAKE ONTARIO WITH
NEARLY STATIONARY MOISTURE STREAMS THAT CONVERGE ACROSS N
NY...PARTICULARLY ALONG THE NORTHEAST EXTENSION ACROSS THE
DEFORMATION ZONE ALONG THE US/CANADA BORDER.  GIVEN STRENGTH OF
CONVERGENCE AND DPVA THERE IS SUFFICIENT ASCENT TO OVERCOME
GENERALLY STABLE ENVIRONMENT FOR EFFICIENT STRATIFORM SHOWERS
CAPABLE OF .5"/HR AT THIS TIME...SATURATING THE GROUND PRECURSORY
TO ADVANCING CONVECTION FROM THE WEST.

GOES-16 10.3UM IR DEPICTS COOLING TOPS INDICATIVE OF DEEPER
CONVECTION ACROSS E ONTARIO REACHING -55C WHICH IS NEAR THE EL
(PER 12Z KBUF SOUNDING)...WITH DPVA COMES MID-LEVEL CAA STEEPENING
THE LAPSE RATES AND SUPPORTING INSTABILITY REACHING 1500 J/KG. 
GIVEN TPW AOA 1.7" EFFICIENCY TO PRODUCE 1.5-1.75"/HR WOULD BE
EXPECTED.  CURRENT TRENDS SUGGEST FORWARD MOTIONS WOULD BE A
LIMITATION FOR TOTALS CAPABLE OF FLASH FLOODING AT THIS TIME (WITH
EXCEPTION SOUTH OF THE MOHAWK VALLEY WHERE FFG VALUES ARE
COMPROMISED).  HOWEVER...AS THE HEIGHT FALLS/MEAN TROF ADVANCES
OVER THE NEXT HOUR OR SO THE SOUTHERN SHORTWAVE WILL CONTINUE TO
LIFT NORTHEAST AND LEAD TO BETTER INCIDENCE FOR THE TROF AND CELL
MOTIONS VECTORS TO STALL/NEAR ZERO FROM SOUTHWESTERN SLOPES OF THE
ADIRONDACK MOUNTAINS TOWARD THE EASTERN PORTION OF LAKE ONTARIO. 
IT IS AT THE PIVOT NEAR LAKE ONTARIO THE GREATEST THREAT WILL
OCCUR WITH RATES OF 1.5"/HR OVER A 2-3HOUR STRETCH POSSIBLE
LEADING TO TOTALS OVER 4".  THOUGH THIS MAY OCCUR NORTH OF THE
BORDER IN CANADA...THE THREAT IS SUFFICIENT FOR FLASH FLOODING TO
BE POSSIBLE ACROSS THE DISCUSSION AREA THROUGH 18Z.

GALLINA

ATTN...WFO...ALY...BGM...BTV...BUF...

ATTN...RFC...MARFC...NERFC...

LAT...LON   45017468 44477400 43217429 42787545 42827656
            43447647 43777639 44167647 44407592 44627560
            44907531